Methods and apparatus for managing location information for movable objects

ABSTRACT

Systems and techniques for locating stored goods. A plurality of fixed contactless identification devices are deployed in an area. Each fixed device exhibits a fixed device identifier that can be read from a distance. Locations within the area are identified through mapping to combinations of fixed device identifiers detected at the location. In addition, a plurality of movable contactless identification devices are associated with goods to be stored and retrieved. Each movable device exhibits a movable device identifier, and movable contactless identification devices are located by identifying a combination of fixed device identifiers received when a movable device identifier is received. The location information may be used independently, or as a supplement to expected location information obtained through other means.

RELATED APPLICATIONS

This application is a Divisional Application of, and claims priority to,U.S. application Ser. No. 11/302,715, filed Dec. 14, 2005, entitled“METHODS AND APPARATUS FOR MANAGING LOCATION INFORMATION FOR MOVABLEOBJECTS,” which is hereby incorporated by reference herein in itsentirety for all purposes. This application is also related to thefollowing other Divisional Application of U.S. application Ser. No.11/302,715, U.S. application Ser. No. 13/721,258.

FIELD OF THE INVENTION

The present invention relates generally to improvements to relativelyefficient storage and retrieval of goods. More particularly, theinvention relates to improved systems and techniques for use ofelectronic devices for providing identification information that can bedetected at a distance and processing the identification information inorder to manage location information for movable objects.

BACKGROUND OF THE INVENTION

Warehousing operations frequently involve stowage and retrieval ofidentified platforms or containers, with each platform or containerbeing associated with identified goods placed or packed on the platformor stored in the container. One commonly used platform for stowage andretrieval of goods is a pallet. Identification of each of a plurality ofpallets is stored and when goods are loaded onto the pallet,identification of these goods is associated with the storedidentification of the pallet. When goods are removed from the pallet,the association of the goods with the pallet is also removed. In thisway, tracking of the location of goods is accomplished by tracking ofthe locations of the pallets onto which the goods are loaded.

Records of locations of pallets are stored in a database. When a palletis needed, a forklift or other retrieval and transporting device isdispatched to the expected location of the pallet. If the pallet is notin the expected location, a search must be conducted. In typicaloperations in a warehouse, retrieval and replacement of pallets iscontinually occurring. Therefore, placement of pallets in incorrectlocations, or incorrect recording of locations of pallets, is likely tooccur with some frequency so that considerable effort and expense mustbe devoted to correcting location information for pallets and findingand relocating incorrectly placed pallets. Even if substantial effort isdevoted to maintaining proper records of locations of pallets andplacing pallets in their proper locations, incorrect storage of palletsand incorrect recording of the locations of pallets is likely to occur.

Warehouse systems frequently employ bar codes to label pallets andlocations in which pallets may be placed. Accurate management of palletlocation information in such a system typically requires that a palletlabel and a location label be scanned whenever a pallet is placed,retrieved, moved, or replaced. If scanning is neglected, or if a scanfails to read a pallet's bar code without the failure being noticed,location information will be incorrect. In addition, bar code systems donot in and of themselves provide easy and convenient notification to anoperator when the operator is approaching a location from which a palletis to be retrieved or to which a pallet is to be restored, and they donot serve to guide an operator to a location.

SUMMARY OF THE INVENTION

Among its several aspects, the present invention addresses such concernsby providing a system of fixed and movable contactless identificationdevices. Each of the fixed and movable contactless identificationdevices provides information uniquely identifying the device. Theinformation can suitably be read at a distance and preferably does notneed to be read along a line of sight. The information provided by afixed device is conveniently referred to as a fixed device identifiersand the information provided by a movable device is convenientlyreferred to as a movable device identifier. Fixed devices need notdiffer from movable devices in design or programming, but the use of theterms “fixed” and “movable” provides a convenient way to distinguish thedevices in terms of the ways they are deployed and used. Fixed devicesare typically affixed to specific, immobile storage locations, such as ashelf or rack in a warehouse. Movable devices are affixed to movableobjects, such as pallets. Thus, movable devices are movable because theyare affixed to movable objects.

The fixed and movable contactless identification devices may beconveniently implemented as radiofrequency identification (RFID) tags,but any device capable of providing information that can be read at adistance without depending on line of sight, may be used. The fixedidentification devices and movable identification devices can be readfrom a distance. In one embodiment of the invention, one of a pluralityof fixed contactless identification devices is attached to each of aplurality of pallets. Each of the fixed contactless identificationdevices provides a fixed device identifier uniquely identifying thefixed device.

Each of the movable contactless identification devices is associatedwith a pallet or container used for the storage and retrieval of goods.Specific descriptions or identifications of goods are suitablyassociated with each pallet or container, so that the location of goodsmay be determined by locating the pallet or container with which thegoods are associated. Fixed device identifier data associated with thefixed contactless identification devices is stored, for example in adatabase, and movable device identifier data associated with the movabledevices is also stored. In addition, location information for the fixedcontactless identification devices may also be stored in associationwith the fixed device identifiers.

Locations of the movable objects, such as pallets, are determined bydetecting fixed device identifiers received at the same time thatmovable device identifiers associated with the movable objects arereceived. A locator may travel about a warehouse, for example,continuously receiving identification signals transmitted from fixed andmovable contactless identification devices. At different locations, thelocator will receive different combinations of device identifiers,because different combinations of fixed devices will be in range of thelocator. In addition, different sequences of fixed device identifierswill be received as the locator moves along different paths. In oneembodiment of the invention, the locations of the fixed contactlessidentification devices are more and more finely resolved as dataaccumulates, so that for most or all movable contactless identificationdevices, the location of the device, and the pallet to which it isaffixed, can be determined through examination of the combination fixeddevice identifiers detected at the same time as movable deviceidentifier transmitted by the movable contactless identification device,together with examination of a record of fixed device identifiersreceived by the locator.

Using information collected by receiving fixed device identifiers andmovable device identifiers, the true locations of movable objects, suchas pallets, associated with the movable device identifiers can bedetermined. The actual location information can be compared againststored expected location information to determine if a pallet is out ofplace. In addition, the locator can read movable contactlessidentification devices in its vicinity to detect when a designatedcontactless identification device, and therefore the pallet to which itis affixed, is in the vicinity of the locator, so that an operator canbe alerted. Further, computed location information for the locator canbe used in conjunction with location information for a desired pallet inorder to identify a path to the pallet and present it to the user. Thepath can be monitored, and a new path computed and presented if adeviation from the original path occurs.

According to another aspect of the invention, the location informationprovided by use of the fixed device identifiers need not supply such ahigh degree of precision and is not depended on to provide locationinformation for movable devices. Instead, the information provided bythe fixed device identifiers may be processed to define zones. The zonein which a movable device identifier is detected may compared againstexpected location information obtained and stored through other means.For example, in a system involving storing and retrieval of pallets,each storage location for a pallet may be associated with a bar code,and each pallet may be associated with a bar code. Precise locationinformation is obtained by reading of a location bar code and a palletbar code from appropriate labels whenever a pallet is retrieved orstored. At the same time, information provided by the fixed and movablecontactless identification devices is constantly being received andprocessed as warehouse operations proceed. The zone in which eachmovable device is detected is noted and compared with storage locationsin the zone. If a movable device is found to be out of the zoneincluding its designated storage location, a discrepancy is detected andnoted. This detection and notation of discrepancies between actual andexpected locations need not involve any operator action. In addition, alocator may be designed so that it is able to search for a movablecontactless identifier. If a user goes to an expected location of apallet and the pallet is not in its expected location, the user maydirect an appropriately designed locator to indicate whether the movablecontactless identification device can be detected within the range ofthe locator. Such a capability aids in searching for missing pallets,and can be performed whether or not a locator is used to collectinformation from fixed contactless identifiers and this information isused to generate location information.

A more complete understanding of the present invention, as well asfurther features and advantages of the invention, will be apparent fromthe following Detailed Description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an environment employing object location managementaccording to an aspect of the present invention;

FIG. 2 illustrates a location information processing center according toan aspect of the present invention;

FIG. 3 illustrates a locator used for detecting signals used indetermining location information and using signals and other informationto locate items; and

FIG. 4 illustrates a process of location determination according to anaspect of the present invention.

DETAILED DESCRIPTION

FIG. 1 illustrates an environment using movable object locationmanagement according to an aspect of the present invention. Theexemplary environment shown is a warehouse 100. The warehouse 100includes a plurality of pallet storage locations 102A-102O. Thelocations 102A-102O are identified by fixed contactless identificationdevices, implemented here in the form of fixed RFID tags 104A-104O,respectively. The fixed tags 104A-104O provide fixed device identifiers,for example, including identifying information such as a serial number.Fixed device identifiers from each of the fixed tags 104A-104O can beread by one or more locators such as the locators 106A-106C at somedistance from the tag, with the distance being determined by factorssuch as the design of the tag, the environment in which the tags areused, the design, position and orientation of the locators 106A-106C andother factors. Only three locators 106A-106C are shown here, but it willbe recognized that any number of locators may be used. The RFID tagsillustrated here are passive tags responding to interrogations by thelocators 106A-106C and providing information through reflectedbackscatter, for example. Such tags provide for low cost and low powerconsumption. However, it will be recognized that any device capable ofemitting identifying information to be received at a distance may beused to implement the present invention.

The locators 106A-106C move through the warehouse 100 during the normalcourse of storage and retrieval of goods in the warehouse 100. Thelocators 106A-106C typically move in numerous different paths, andtherefore can be expected to receive numerous different combinations ofsignals from various combinations of the fixed tags 104A-104O, as thelocators 106A-106C move through positions in range of differentcombinations of tags. As will be discussed in greater detail below, aseach of the locators 106A-106C detects tags and receives theiridentifiers, the locator transmits the combination of identifiers thatare received at any particular time to a server (not shown here, butillustrated in FIG. 2 and discussed below), where the information can beanalyzed in order to establish correlations between identifiers receivedfrom different combinations of the fixed tags 104A-104O and locations inthe warehouse 100 where these combinations of identifiers will bedetected.

For example, suppose that the locator 106A is placed at the location108. At the location 108, the locator 106A receives signals from thefixed tags 104A, 104F, 104B and 104G. The locator 106A then travels tothe location 110, where it receives fixed device identifiers from thefixed tags 104B, 104C, 104G and 104H, and then to the location 112,where it receives fixed device identifiers from the fixed tags 104L and104M. The location of the locator 106A at any particular time can beisolated by identifying the combination of identifying signals that itdetects at that time and comparing that combination of signals against astored map or table of signal combinations versus locations. Thelocators 106B and 106C are typically moving along different paths at thesame time and their positions may be determined in a similar way. Theposition of the locators 106A-106C may be computed with greater orlesser precision, depending on the design of the locators, the warehouseenvironment and the various tags. Depending on the precision of positioncomputation for the locators 106A-106C and various other design choicesand constraints, such as the desired degree of involvement by operators,the location information provided by the locators may be used forretrieval and location of goods or may be used to supplement locationinformation collected in some other way, such as through reading of barcodes associated with storage locations.

Goods are stored in the warehouse 100, with an assembly of goodstypically placed on a pallet, which is then stored in one of thelocations 102A-102O. Pallets 114A-114O are illustrated here, with thepallets 114A-114O initially stored in the locations 102A-102O,respectively. Each of the pallets 114A-114O has a movable contactlessidentification device affixed thereto. Each movable contactlessidentification device transmits movable device identifiers includinginformation uniquely identifying the device. In the exemplary embodimentillustrated here, each movable contactless identification device isimplemented as an RFID tag, with the RFID tags 116A-116O affixed to thepallets 114A-114O, respectively. The tags 116A-116O may conveniently bereferred to as pallet tags, to distinguish them from the fixed tags104A-104O. As various ones of the pallets 114A-114O are retrieved fromand stored in one or another of the storage locations 102A-102O, themovable device identifiers provided by the pallet tags 116A-116O can bedetected, as well as various ones of the fixed tags 104A-104O. Aplurality of transport devices, such as the forklifts 118A-118C, may beequipped with the locators 106A-106C, respectively, and in the course ofoperations the locators 106A-106C may be used to detect different onesof the pallet tags 116A-116O that come within range, as well as thefixed tags in their vicinity. Alternatively, one or more of the locators106A-106C, or similar locators, may be handcarried by operators wakingfrom one location to another, for example to retrieve goods to becarried by hand or on a manual transport device such as a cart. As afurther alternative, the locators 106A-106C or similar locators may beused to guide the movement of automated or remotely controlled transportdevices. Detection of pallet tags, together with location informationdetermined for locators, may be used to help manage warehouseoperations. For example, if an operator is replacing a pallet, thedesignated storage location of the pallet may be compared against theposition of the locator carried by the operator. If the operator isnearing an incorrect storage location for the pallet, the operator maybe advised of the correct storage location.

Detection of pallet tags need not be, and preferably is not, confined todetection of tags affixed to a pallet that is being worked with at aparticular time. Instead, detection and noting of pallet tags, togetherwith the combinations of fixed tags in their vicinity, is preferablycarried out continuously, in order to perform a continuous automatedaudit of pallet locations.

FIG. 2 illustrates a location information processing center 200according to an aspect of the present invention. The center 200 maysuitably be placed in the warehouse 100 of FIG. 1, but may alternativelybe placed in a remote location, provided that a communication link isestablished allowing for communication between the center 200 andlocators such as the locators 106A-106C of FIG. 1.

The center 200 preferably includes a data processing server 202 forstoring and processing information used in management of operationscarried out in the warehouse 100. The server 202 suitably includes aprocessor 204, high speed memory 206, and long term storage such as ahard drive 208. The server 202 includes an operator interface 210,comprising a keyboard 212, display 214 and printer 216. The server 202is connected to a locator interface 218 for managing communication withthe locators 106A-106C of FIG. 1 and other similar locators. The locatorinterface 218 includes a wired connector 220 to allow connection to alocator for uploading and downloading of information, and a wirelessinterface 222 to allow for wireless communication with locators, forexample when locators are being used in operations in the warehouse 100.The locator interface 218 may be incorporated into or directly connectedto the server 206, or may communicate with the server 206 through anintermediary connection, such as a local area network 224.

The server 202 hosts a location analysis and management module 225. Themodule 225 preferably takes the form of software residing on the harddrive 208, which is transferred into the high speed memory for use bythe processor 204 as needed. The server 202 also hosts a number ofdatabases 226-232, resident on the hard drive 208 and transferred intoand out of the high speed memory 206 as needed. The databases 226-232are used and maintained by the module 225. The databases 226-232 includea fixed tag database 226, a pallet tag database 228, a warehouse model230 for use in determining relationships between signal combinations andphysical locations in the warehouse, and a signal combination tolocation map 232.

The fixed tag database 226 stores information relating to the fixedtags, and comprises entries 250A . . . 250O for the fixed tags104A-104O, respectively, of FIG. 1. Each of the entries 250A-250Oincludes a record of the identifier stored in the associated tag, alongwith location information identifying the tag's physical location. Theentry 250A is shown in detail, and includes the tag's serial number anda set of location coordinates. The location coordinates are preferablyalso used by the model 230.

The pallet tag database 228 comprises entries 252A . . . 252O for thepallet tags 116A-116O, respectively, of FIG. 1. Each entry includesrecords for the identifier for the associated pallet tag, location dataindicating the assigned location of the pallet associated with the tag,and identifiers for fixed tags in the vicinity of the assigned locationof the pallet tag. Each entry may also include a record for an actuallocation of the pallet tag. If desired, the record may reflect theactual location of the pallet tag, whatever that location happens to be.Alternatively, the record of the actual location may be blank if thereis no indication that the pallet is out of its assigned location, butmay be populated with data indicating the actual location of the palletif the pallet is found to be in a location other than the assignedlocation. Each entry also suitably includes a description of the itemsloaded onto the pallet. This description may be a general description ofthe type and quantity of goods. Particularly in the case of valuableitems, however, the description may also include specific identificationof goods, such as a serial number or numbers of an item or items. Theentry 252A is shown in detail.

The warehouse model 230 includes records defining the layout of thewarehouse 100, such as a list of designated pallet storage locations,sizes of storage locations and placement of tags in the storagelocations. The model 230 also suitably includes information such asdistances between locations, relative directions from one location toanother, placement of corridors between storage locations and otherinformation helping to define the use of space within the warehouse 100.The server 202 uses the warehouse model 230 to help interpret signalsreceived from fixed tags. For example, the locator 106A may receiveidentifiers from three fixed tags. Analyzing the identifiers in light ofthe information of the warehouse model defining the distances betweenthe storage locations to which the tags are affixed and the relativedirections between storage locations helps to identify the position atwhich the combination of signals is received.

The signal combination to location map 232 is created and refined usinginformation from the locators 106A-106C and similar locators. As alocator arrives at a known location, for example a location of acorrectly placed pallet, the locator may transmit to the server 202 anotation of the location and of the signals received at the location.For example, the locator may allow for a user to note that he or she hasarrived at a location and retrieved a pallet. The user may explicitlynote that no discrepancy exists between the expected location and theactual location. Alternatively, an indication of a retrieval with nonotation of a discrepancy may be presumed to indicate that nodiscrepancy exists. Whenever a locator sends an indication that it is ata known location along with the signals received at the location, thelocation analysis and management module 225 may use this information torefine the signal combination to location map 232.

Retrieval and storage of the pallets 114A-114O is accomplished bytransport devices, for example, the forklifts 118A-118C of FIG. 1. Alocator is suitably affixed to or carried on each transport device. Inthe present exemplary case, the locators 106A-106C are shown as beingcarried on the forklifts 118A-118C, respectively. Each of the locatorsis able to communicate with the server 202 as it moves. When a locatordetects a signal from one of the fixed tags 104A-104N, the locator isable to transmit the identifier received from the tag and to continue totransmit the identifier so long as it is detected. If more than oneidentifier is detected, all identifiers may be transmitted as they arereceived. This information is used in conjunction with the fixed tagdatabase 226 and the model 230 to construct and refine the signal map232 on an ongoing basis. The signal map 232 associates locations withcombinations of signals detected at the locations.

Particularly useful information is provided by one of the locators106A-106C when the locator is at a known location. For example, if theforklift 118A is used to retrieve a pallet that is in its expectedlocation, the location of the locator 106A can be known with certaintywhen the locator is at the location of the pallet. At that time, thelocator 106A may transmit to the server 202 a notation of the locationand of the signals received at the location. For example, the locator106A may allow for a user to note that he or she has arrived at alocation and retrieved a pallet. The user may explicitly note that nodiscrepancy exists between the expected location and the actuallocation. Alternatively, an indication that a pallet is being retrieved,with no notation of a discrepancy, may be presumed to indicate that nodiscrepancy exists.

Whenever a locator sends an indication that it is at a known locationalong with the signals received at the location, the location analysisand management module 225 may use this information in creating orrefining the signal combination to location map 232. Once the signal tolocation map 232 is created, combinations of signals received can beused to identify the position of each of the locators 106A-106C. Inaddition, by tracking the combinations of signals received over time,the paths of the locators 106A-106C can be tracked. Tracking the path ofthe locators helps to resolve ambiguous position calculations.

The locators 106A-106C and other locators also receive signals from thepallet tags 116A-116O as the locators move around the warehouse 100. Aseach of the pallet tags 116A-116O is detected by a locator, the locatortransmits to the server 202 the identifier of the detected pallet tag aswell as all identifiers of fixed tags 104A-104O that are detected at thesame time. If a signal from one fixed tag is lost and another isacquired, the transmission to the server is changed to reflect the newinformation. In this way, a locator is able to provide the server 202with information showing which pallet tags are in the vicinity of whichfixed tags.

Once the location of a pallet tag is identified, the location asdetected may be compared against the location as entered in the pallettag database 228. If a pallet is out of place, this fact, and thelocation of the pallet, may be noted and reported. For example, alocation discrepancy database 252 may be compiled and stored. Thedatabase 252 may be examined and a report prepared periodically.Alternatively or in addition, the actual location of the pallet tag maybe stored in the pallet tag database 228. Incorrect placements ofpallets may be identified by surveying the database 228, comparing theactual location of a tag against its assigned location and reportingdiscrepancies As a further alternative, where storage of a pallet in aspecific location is not critical, the assigned location record for apallet may simply be updated to reflect the actual location of thepallet.

In addition, knowledge of the positions of locators and pallets may beused to guide operations. For example, an operator may be directed tothe correct location of a pallet or advised when about to store a palletin an incorrect location. In addition, the positions of locators may bemonitored and this information used to prevent traffic conflicts bywarning operators of traffic bottlenecks. In addition, knowledge ofpallet locations, operator positions and positions of other operatorsand equipment may be used to provide routing instructions, guidingoperators to locations based on considerations of minimum distances aswell as traffic avoidance.

The location analysis and management module 225 is operative to examineone or more of the various databases 226-232 and 252 in order to performanalyses and provide information needed by users. For example, themodule 225 may periodically examine the databases 228 and 252 toidentify misplaced pallets, and prepare reports identifying misplacedpallets. The reports may suitably identify each misplaced pallet, aswell as the actual and expected locations of the misplaced pallet.

If desired, the location discrepancy database 252 may note the time eachdiscrepancy is discovered and store the time of discovery as part of arecord of a discrepancy. For convenience, the discrepancy database 252may be updated when discrepancies are corrected. However, in order toprovide for an understanding of the operations of the warehouse 100, adiscrepancy history database 254 may also be maintained. The discrepancyhistory database 254 includes a notation of each discovered discrepancy,the time of discovery, and the time of correction, if any. The module225 may examine the discrepancy database 252 and the discrepancy historydatabase 254 in order to generate reports of discrepancies and theircorrections. A user may submit parameters defining a time period andsection of the warehouse 100 to be covered by the report, and the module225 examines the databases 252 and 254 in order to generate lists ofdiscrepancies meeting those parameters.

The center 200 may also furnish information to guide users in locatingmisplaced or correctly placed pallets, or in identifying the correctlocation of a pallet to be stored. A user working at retrieving andreplacing pallets may use the locator 106A to enter an identifier for adesired pallet. The locator 106 transmits the identifier to the center200, where it is passed to the module 225. The module 225 searches thepallet database 228 and the discrepancy database 252 to find thelocation of the identified pallet. If the locator 106A has beentransmitting its received signals to the center 200 while the user hasbeen conducting operations, the center 200 may store thesetransmissions, for example in a locator transmissions buffer 256, andanalyze the received signals using the signal to location table 232 inorder to find the position of the locator 106A. The module 225 then usesthe warehouse model 230 to determine a path between the location of thelocator 106A and the location of the identified pallet and to transmitdirections to the locator 106A. The module 225 may also determine thepositions and paths of the locators 106B and 106C in order to taketraffic considerations into account in generating directions.

Similarly, a user who retrieves a pallet can enter the pallet'sidentifier using the locator 106A, or another locator. The locator 106Atransmits the identification of the pallet to the center 200, and themodule 225 identifies the pallets storage location and computes andtransmits directions to the storage location.

In addition or as an alternative to identification of pallets by a user,a list of pallets to be retrieved may be transmitted or otherwiseprovided to each of the locators 106A-106C. If desired, the same listmay be transmitted to all locators, with the list being updated for alllocators whenever a pallet is retrieved. When a pallet is found, a usermay make an appropriate selection, such as pressing a “located” key toindicate that the identified pallet has been found. As will be discussedfurther below, the locators 106A-106C provide a user with a number ofalternatives for navigating through a list.

The discussion above describes the system 100 as being usedindependently to compute locations of pallets and to provide locationinformation to operators. However, the various tags and locators, andthe server 202, may alternatively be used to supplement locationinformation gathered and stored in other ways. For example, location ofpallets may be tracked using bar coded labels on pallets and on palletstorage locations. In addition, a plurality of fixed contactlessidentifiers such as the fixed tags described above may be placed in anarea, and movable contactless identifiers such as the movable tagsdescribed above may be affixed to each pallet. However, if informationgathered from the fixed tags and movable tags is used as a supplementalsource of information, precise location information need not be computedusing information gathered from the fixed tags and the movable tags. Insuch a system, the server 202 may also host an expected locationinformation database 258. In the present exemplary embodiment, theexpected location information database 258 stores bar code informationfor each storage location. Bar code information for each storagelocation is stored in association with bar code information for a palletstored in the location. The bar code information for the storagelocations and pallets may be collected in conventional ways, such asmanual reading of a storage location bar code and a pallet bar code bymaking appropriate scans with a bar code reader whenever a pallet isstored or retrieved. In this case, the server 202 also hosts a movabledevice identifier to bar code correlation database 260. The database 260allows for easy retrieval of the bar code identifier for a pallet upondetection of the pallet's movable device identifier, or vice versa.

In order to use the location information provided by use and analysis ofcontactless identifiers as a supplement to another system of collectinglocation information, such as a bar code system, the pallet tag database228 would not necessarily need to include precise location information,but might instead include a broader category of information for thelocation of each pallet tag, for example a zone in which the pallet tagwas found. Alternatively, this information might not be stored in thepallet tag database 228, but might be stored instead in the locationdiscrepancy database 252. In such a case, the server 202 would identifythe zone in which a pallet tag was located whenever a report ofdetection of the movable device identifier associated with the tag wasreceived. A comparison would be made against the expected locationdatabase 258. If the expected location of the pallet to which the tagwas affixed was not included in the zone in which the tag was detected,the location discrepancy database 252 would be consulted. If thelocation discrepancy database did not already include the discrepancy,the database 252 would be updated.

FIG. 3 illustrates additional details of the locator 106A. The locators106B and 106C are not shown, but are similar. The locator 106A includesa display screen 302, a keypad 304, a tag communication interface 306and a server communication interface 308. The server communicationinterface 308 includes a wireless interface 310 and an input/output port312. The locator 106A also includes a processor 314, high speed memory316 and long term storage 318. The long term storage hosts a tagcommunication module 320, a server communication module 322, an operatorinterface module 324 and a transport interface module 326, described infurther detail below. The software modules 320, 322, 324 and 326 aretransferred to the high speed memory 316 for execution by the processor314 as needed.

The keypad 304 includes a number pad 328 and various control keys, suchas cursor keys 330A and 330B, an “enter” key 332, a “located” key 334and a “not found” key 336.

The locator 106A uses the tag communication interface 306 to receiveidentification messages from fixed tags such as the tags 104A, . . . ,104O and the pallet tags 116A, . . . , 116O. Communication suitablyoperates under the control of the tag communication module 320. Thecommunication interface 306 may transmit query signals, for example,interrogation signals for passive RFID tags, allowing for the use of lowcost passive RFID tags as the tags 104A, . . . , 104O and the tags 116A,. . . , 116O. The communication interface 306 receives identifyingmessages from the tags, which are then stored in memory 316 for analysisby the tag communication module 320. Once the analysis is performed,preparation and transmission of appropriate messages to the center 200is directed by the server communication module 322, using the servercommunication interface 308. The server communication module 322preferably directs transmission of received tag identifiers at suitableintervals, with the time that each tag identifier was received beingsent to the center 200 of FIG. 2 as part of the transmission. As notedabove, the module 225 of FIG. 2 uses information received from thelocator 106 and other similar locators to determine the position of thelocator 106A and of the pallet tags whose identifiers were received.

The locator 106A receives selections and identifiers of pallets to beretrieved, for example by entries made by a user employing the numberpad 328 and control keys on the keypad 304, or transmissions receivedfrom the center 200. For example, a list of pallets to be retrieved maybe transmitted through a wireless connection with the center 200, or maybe downloaded to the locator 106A through a direct or mediated wiredconnection between the locator 106A and the center 200.

Once the identifier or identifiers are entered or received, a list 338of the identifiers are stored in the memory 316. A list 340 of theentered identifiers is shown on the display 302. In the illustratedexemplary case, the list 338 is larger than the display 302 is designedto show, so the displayed list 340 includes only a portion of the storedlist 328. A user may scroll up and down through the displayed list 340as desired to see any identifier desired, and may select entries on thedisplayed list 340 using appropriate keys on the keypad 304. When a userhas entered or selected a pallet to be retrieved, or when a pallet thatis to be retrieved has otherwise been identified, the operator interfacemodule 324 notes the identifier of the designated pallet, which is sentby the server communication module 322 to the center 200, with anindication that the pallet is to be retrieved. The center 200 identifiesthe location of the locator 106 using the tag identifiers that have beentransmitted to the center 200, identifies the location of the identifiedpallet and transmits directions to the locator 106. The directions arereceived by the server communication module 322, where they areformatted and displayed on the display 302 under the control of theoperator interface module 326.

When a pallet is retrieved, the user may indicate that the pallet hasbeen retrieved by making an appropriate keypad entry. The user may pressthe “located” key 334 to direct transmission of an indication to thecenter 200 that the pallet has been retrieved. The indication issuitably accompanied by identifiers of the tags, particularly the fixedtags, from which signals are being received at the time the retrieval isindicated. Alternatively, if the pallet is not in the location to whichthe user has been directed, the user may press the “not found” key 336to indicate that the pallet is not present at the location. The module225 of the center 200 may then update the discrepancy database 252 andthe pallet database 228 to reflect this information.

In addition or as an alternative to updating the discrepancy database252 and the pallet database 228 the locator 106A may operateindependently to search for a contactless identification deviceassociated with a pallet that is not found in its expected location.When a user presses the “not found” key 336, the locator 106A mayexamine all device identifiers that are detected within range and mayaccess the pallet database 228 in order to determine whether any deviceidentifier matches the movable device identifier associated with thepallet that has not been found. If the device identifier is detected,the locator 106A may display a message or otherwise issue an alert thatthe missing pallet is in the vicinity. This mode of operation may beimplemented in any way desired. For example, a search in the immediatevicinity of the expected location of the missing pallet may beconducted, or the search may continue until an alternative mode ofoperation is selected by the user. A continued search allows the user tomove through the area in an attempt to detect the missing pallet,relying on the locator 106A to provide an indication when the pallet isin the vicinity and conducting a more focused search only when such anindication is received. Such a mode of operation may be particularlyuseful in cases in which information from contactless identificationdevices is used only as a supplement to location information generatedin some other way, such as reading of bar codes. In such a case, if auser is directed to an expected storage location for a pallet and thepallet is not found, the user may use the locator 106A to search withinits range for the contactless identification device associated with themissing pallet.

As an alternative or in addition to displaying identifiers anddirections using the display 302, the locator 106A may include atransport device interface 342, operating under the control of thetransport interface module 326. The transport device interface 342 issuitably connected to, or wirelessly communicates with, a matinginterface built into an automated or remotely controlled transportdevice and provides information and commands needed by the device, andreceives information provided by the device. The information may bewirelessly passed between the locator 106 and the center 200. Forexample, the locator 106 may receive travel directions from the center200 describing a route to be followed to locate and retrieve a specificpallet. The locator 106 transmits motion commands to an automatedtransport device through the transport device interface 342.

FIG. 4 illustrates the steps of a process 400 of goods locationmanagement according to an aspect of the present invention. The process400 may suitably be carried out using a system such as the system 100illustrated in FIG. 1. At step 402, a plurality of fixed contactlessidentification devices is deployed about an area, which for purposes ofexample will be assumed to be a warehouse. The contactlessidentification devices may suitably be low cost passive devices such asRFID tags, but any type of device capable of transmitting an identifyingsignal may be used. At step 404, data structure mapping occurs forcombinations of fixed device identifiers emitted by the fixed devicesagainst locations within the warehouse. The data structure may be builtby moving a locator from one location to another and recording the fixeddevice identifiers that are received during movement of the locator,particularly when the locator is at a known location. Other ways ofbuilding the data structure may be contemplated, for example using knowninformation about the warehouse in which the fixed contactlessidentification devices are deployed and the nature of the signalsemitted by the identifiers to compute relationships between locationsand signal combinations.

At step 406, a plurality of movable contactless identification devicesare associated with movable objects to be stored in or retrieved fromdefined locations in the area. The movable contactless identificationdevices may be affixed to containers or platforms in or on which goodsare to be placed. For example, a plurality of pallets may be used in awarehouse, with a movable contactless identification device affixed toeach pallet. A record of each movable contactless identification deviceis stored in a database. For convenience, in the remainder of thisdiscussion it will be assumed that the movable contactlessidentification devices are affixed to pallets.

At step 408, pallets bearing affixed movable contactless identificationdevices are placed in designated locations in the warehouse. Each palletmay be associated with a location in which it is placed, and thereforethe movable contactless identification device is also associated withthat location. In this way, a list of records is created in whichdesignated pallets are expected to be found, with the presence of apallet being detectable through a signal emitted by the movablecontactless identification device associated with the pallet. At step410, one or more locators is moved about the warehouse, for exampleduring retrieval and storage of pallets. As each locator moves, itreceives fixed device identifiers and the received fixed deviceidentifiers are identified and processed to identify the location of thelocator, and the path traveled by the locator, at different times.During the same time period, the locator receives signals from movabledevice identifiers emitted by movable contactless identificationdevices. When movable device identifier is received, the combinationfixed device identifiers received at the same time is noted, as is thecomputed position of the locator. This information is analyzed toidentify the location of the movable contactless identification deviceemitting the movable device identifier.

At step 412, upon identification of a pallet to be retrieved, thelocation of the pallet is provided to a user. Directions to the locationmay also be provided. Similarly, upon identification of a pallet to berestored to its location, identification of the location and directionsto the location may also be provided.

At step 414, whenever a pallet is retrieved from or restored to itsdesignated location, or when a pallet is found in an improper locationor has failed to be found in its expected location, an indication of theretrieval, storage, or failure to find the pallet is noted and used toupdate position and comparison information. The actual location in whichthe pallet is found or replaced may be provided, particularly when thepallet is found outside of its designated location.

At step 416, the actual positions of movable identifiers, and thepallets with which they are associated, are compared to their expectedpositions and discrepancies noted. At step 418, comparisons of theactual position information with expected position information arereported as needed. For example, periodic reports of misplaced palletsmay be prepared. In addition, evaluations of the proportion of misplacedpallets over a specified time within the entire warehouse or in aspecified area of the warehouse may be generated.

While the present invention is disclosed in the context of a presentlypreferred embodiment, it will be recognized that a wide variety ofimplementations may be employed by persons of ordinary skill in the artconsistent with the above discussion and the claims which follow below.

We claim:
 1. A locator for use in locating objects having attachedmovable contactless identification devices, each movable contactlessidentification device exhibiting a movable device identifier,comprising: an identifier communication interface for reading themovable device identifiers; server communication interface forcommunicating with a data processing server storing records of themovable device identifiers; and a control unit for processing movabledevice identifiers read within the vicinity of the locator to determineif a specified movable device identifier is present in the vicinity ofthe locator; wherein the identifier communication interface also readsfixed device identifiers exhibited by fixed contactless identificationdevices, wherein the server communication interface also communicateswith a data processing server storing records of the fixed deviceidentifiers, and wherein the control unit is further operative toprocess movable device identifiers and fixed device identifiers receivedfrom movable contactless identification devices in the vicinity of themovable contactless identification devices from which movable deviceidentifiers are received to identify locations of the movablecontactless identification devices.
 2. The locator of claim 1, whereinthe locator transmits fixed device identifiers to the data processingserver as the locator moves from one location to another.
 3. The locatorof claim 2, wherein the locator transmits to the data processing centerfixed device identifiers read from fixed contactless identificationdevices in the vicinity of the movable devices from which movable deviceidentifiers are received.
 4. The locator of claim 3, wherein the locatortransmits to the data processing server a selection designating anobject to be located and receives direction information from the server,the direction information being based on a position of the locatorcomputed from current and historical information showing fixed deviceidentifiers received by the server and on a computed location of amovable contactless identification device affixed to the object.